Some people swear by aliens, some swear by TCU's. I have both on my rack. I think the aliens are a little nicer, but they are often hard to track down. I've only seen them reguarly in North Conway, Keene Valley and the Gunks. I love every alien that I have and I get a nice warm feeling once one goes in. TCU's are really nice too. They are a lot easier to find, and you can even get them on sale. Good luck trying to find an alien on sale. One inherrent limitiation in three cam design is that they can sometimes pivot around. Not so good, but if you use slings or at least draws then you should be set. They do have cam stops if you are worried about that.
The zeros look really nice in the store, but a partner of mine has some that aren't holding up as well. The action is really rough and they just don't inspire the same confidence. In the really small (keychain toy size) they are your only choice.
Maybe I'm missing the point of cam stops, but I don't see them as such a vital feature. I imagine a lot of the cam stop hype stemmed from the BD cammalot design which has integral cam stops. I speculate that a lot companies added them to keep up with the jones's. Although cam stops might be usefull in placing a #3 cammalot like a nut, why would you unless you were totaly desperate? If you cam does walk into a crack and open up, the cam stops might keep it in, but again, not a good situation. IMHO, with the small cams, if you place one and need to rely on the cam stops you have already 'effed up and shouldn't have made that placement. I also understand that in desperate situations (or situations that feel more desperate than they are
) the gripped factor tends to lead to somewhat inventive placements where cam stops might come into play. To cut to the chase, cam stops don't hurt, but I've never gotten to a ledge and said "thank god I had good cam stops" I think I just sucsessfuly taunted the gear gods enough to make this weekend interesting.